This invention relates generally to a conveyor ratcheting apparatus for advancing a conveyor in one direction in discrete steps.
Conveyor ratcheting apparati for advancing conveyors in one direction in discrete steps are known in the art. A typical conveyor ratcheting apparatus includes an indexer that operatively connects to and drives a conveyor over discrete distances to align or index objects supported on the conveyor with consecutive work stations. For example, a plurality of pallets may be supported on the conveyor and the indexer drives the conveyor intermittently to move the pallets to dwell positions at one or more work stations disposed along the conveyor. The indexer may include a ratchet arm pivotally supported on a main shaft that is in turn supported on a frame. Ratchet arms are generally supported for pivotal movement relative to the frame through an arc of approximately 90 degrees. It is known to drive such a ratchet arm through its arc using a linear actuator such as a hydraulic or pneumatic cylinder. It is also known for a conveyor ratcheting apparatus to include a ratchet wheel having teeth formed at spaced locations around an outer circumference of the ratchet wheel. The ratchet arm of such an apparatus generally includes a pawl that engages the teeth and causes the ratchet wheel to rotate in one direction as the ratchet arm moves in one direction through its arc and disengage from the teeth as the ratchet arm reverses direction along the same arc.
One problem experienced with conveyor ratcheting apparati of this type is that they may be unable to positively hold an indexing drive mechanism in its dwell or stopped positions rigidly enough to suit certain applications. This inability to positively stop conveyor motion is often due to the significant moment of inertia generated by a moving, laden conveyor. It is also difficult to positively lock an indexing drive against reactive forces that a conveyor can apply to the indexing drive once stoppedxe2x80x94forces that otherwise tend to shift the conveyor out of desired dwell positions.
To provide improved rigidity in conveyor dwell positions, the assignee designed a conveyor ratcheting apparatus includes a frame and a ratchet arm supported on a main shaft on the frame for pivotal movement relative to the frame between first and second angularly-spaced positions. The ratchet arm is driven between the first and second positions (an angular distance of approximately 90 degrees) by a ratchet arm actuator cylinder. This conveyor ratcheting apparatus includes a ratchet drive wheel rotatably supported on the main shaft adjacent the ratchet arm. The ratchet drive wheel is configured to drivingly connect to a conveyor drive wheel via a chain loop. The ratchet drive wheel includes four circumferentially-spaced axially-oriented pin receiving holes. A drive pin actuator cylinder extends a drive pin through a hole in the ratchet arm and into one of the pin receiving holes in the ratchet drive wheel when the arm is in the first position. The drive pin actuator cylinder retracts the drive pin when the arm is in the second position. The drive pin actuator cylinder therefore allows the ratchet arm to rotate the ratchet wheel in only one direction and only when the arm moves from the first to the second position. A locking pin actuator cylinder is also fixed to the frame. The locking pin actuator cylinder extends a locking pin into one of the pin receiving holes whenever the ratchet arm reaches the second position. The locking pin actuator also retracts the locking pin whenever the arm has returned to the first position. The locking pin positively locks the ratchet drive wheel against rotation and the attached conveyor against movement while the arm is returning to the first position from the second position.
What is needed is a conveyor ratcheting apparatus that can accurately and positively hold an indexing drive mechanism and an attached laden conveyor in dwell positions despite the significant moment of inertia generated by such a conveyor and despite any reactive forces that the conveyor may apply to the indexing drive once stopped. What is also needed is such a conveyor ratcheting apparatus that is robust and easy to construct and operate.
The invention is a conveyor ratcheting apparatus for advancing a conveyor in one direction in discrete steps. The apparatus includes a first ratchet arm pivotally supported on a frame for movement relative to the frame between first and second radially-spaced positions. The ratchet arm is configured to be driven between the first and second positions by a ratchet actuator. The conveyor ratcheting apparatus also includes a ratchet wheel rotatably supported on the frame and including at least two circumferentially spaced teeth. The ratchet arm is configured to sequentially engage each of the teeth and to cause the ratchet wheel to rotate in one direction each time the ratchet arm engages one of the teeth and moves toward the second position from the first position. The ratchet arm is configured to disengage each time the ratchet arm moves from the second position to return to the first position. A first ratchet wheel stop detent is formed in the ratchet wheel. A detent engagement member is movably supported on the frame in a position to be moveable into engagement with the first ratchet wheel stop detent when the first ratchet arm is in the second position. The detent engagement member is configured to positively hold the ratchet wheel when engaged with the first ratchet wheel stop detent and to allow ratchet wheel rotation out of the second position only after being disengaged from the ratchet wheel stop detent. An actuator is operatively connected to the detent engagement member and is configured to disengage the detent engagement member from the ratchet wheel stop detent before the ratchet wheel is rotated out of the second position. The actuator is configured to disengage the detent engagement member from the ratchet wheel stop detent in response to ratchet arm movement.
Objects, features and advantages of this invention include the ability to accurately and positively hold an indexing drive mechanism in its dwell positions without using a complex externally-driven actuator system, eliminating the need for an external actuator drive mechanism to engage the detent engagement member, and reducing the number and complexity of components that must be purchased or fabricated to positively hold a conveyor in its dwell positions.